Influence of sp³–sp² Carbon Nanodomains on Metal/Support Interaction, Catalyst Durability, and Catalytic Activity for the Oxygen Reduction Reaction

In this work, platinum nanoparticles were impregnated by two different techniques, namely the carbonyl chemical route and photodeposition, onto systematically surface-modified multiwalled carbon nanotubes. The different interactions between platinum nanoparticles with sp²–sp³ carbon nanodomains were investigated. The oxidation of an adsorbed monolayer of carbon monoxide, used to probe electronic catalytic modification, suggests a selective nucleation of platinum nanoparticles onto sp² carbon nanodomains when photodeposition synthesis is carried out. XPS attests the catalytic center electronic modification obtained by photodeposition. DFT calculations were used to determine the interaction energy of a Pt cluster with sp² and sp³ carbon surfaces as well as with oxidized ones. The interaction energy and electronic structure of the platinum cluster presents dramatic changes as a function of the support surface chemistry, which also modifies its catalytic properties evaluated by the interaction with CO. The interaction energy was calculated to be 8-fold higher on sp³ and oxidized surfaces in comparison to sp² domains. Accelerated Stability Test (AST) was applied only on the electronic-modified materials to evaluate the active phase degradation and their activity toward oxygen reduction reaction (ORR). The stability of photodeposited materials is correlated with the surface chemical nature of supports indicating that platinum nanoparticles supported onto multiwalled carbon nanotubes with the highest sp² character show the higher stability and activity toward ORR

Spectroelectrochemical Probing of the Strong Interaction between Platinum Nanoparticles and Graphitic Domains of Carbon

This study focuses on clarifying the strong interaction existing between extended graphitic domains of ordered carbonaceous materials such as multiwalled carbon nanotubes and platinum nanoparticles. This interaction results from the heterogeneous nucleation of platinum nanoparticles onto the carbon support. The metal clusters are chemically synthesized by using the carbonyl route. Two different carbon supports are used namely, homemade multiwalled carbon nanotubes, MWCNT-m, and classical Vulcan XC-72. Physicochemical properties of these materials are described by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The effect of the strong interaction on the electronic properties of platinum nanoparticles is electrochemically probed by means of CO stripping experiments coupled with <i>in situ</i> Fourier transform infrared spectroscopy (FTIR). Density functional theory (DFT) is used to evaluate changes to the electronic structure of a platinum cluster interacting with a graphite substrate and their effects on CO adsorption on the cluster. Results are correlated with structural and electronic properties of platinum nanoparticles. The stability of Pt/carbon catalysts under electrochemical potential cycling is correlated with the properties of carbon substrates